Holding devices of this type are often required in performing surgical procedures in order to hold medical instruments of various types, such as retractors, video cameras or endoscopes, in a particular position for extended periods. Thanks to the jointed configuration of the holding devices it is possible for the surgeon to precisely position the medical instrument held by the bracket and to fix the selected position of the holding device by blocking the joint or joints of the bracket.
A generic holding device is known for example from DE 295 21 305 U1. In this known holding device, the pivot ball is pressed against the bearing shell by a spring-loaded pressure plate, which in turn constitutes a part of the bearing shell. To block the joint, the pressure plate is coupled with a piezoelectric actuator that expands on the application of electric current and thus increases the pressure of the pressure plate on the pivot ball until the pivot ball is affixed by clamping.
With this known structure it is possible to affix the ball and socket joint securely, but the structure has the disadvantage that it is no longer possible to block the joint in the event of a power failure. In addition, structures with a partial spring-loaded bearing shell have the disadvantage that with an axial force on the pivot ball that is directed against the force direction of the spring-loaded bearing shell, the joint can unintentionally be released.